Method of and bath for electrodepositing tungsten alloys



Patented Sept. 22, 1953 METHOD OF AND BATH FOR ELECTRO- DEPOSITING TUNGSTEN ALLOYS Abner Brenner, Chevy Chase, Md., Polly S. Burkhead, Bethlehem, Pa., and Clara A. Sentel, Herndon, Va., assignors to the United States of America as represented by the Secretary of War No Drawing. Application November 8, 1946, Serial No. 708,566

12 Claims.

(Granted under Title 35, U. S.

sec. 266) l The invention described in the following specification and claims may be manufactured and used by or for the United States Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a method and composition for electrodepositing tungsten alloys, and it has particular reference to the plating of tungsten alloyed with metals of the iron group including iron, cobalt and nickel.

Broadly stated, a principal object of our in ention is to provide a simple, direct and highly effective method for electrodepositing alloys of tungsten with one or more metals of the iron group.

A more specific object is to provide suitable baths for the electrodeposition of tun sten in alloy with one or more metals of the iron group, and which are characterized by high current effciency, good throwing power, and stability in operation.

Another object is to provide a reliable method and means for obtaining electrodeposition of a tungsten alloy of uniform thickness and composition, and whose surface is free of nodules, pits and blemishes.

Still another object is to provide a method and means for obtaining an electroplated alloy of tungsten which possesses high cohesive and adhesive properties and therefore will not peel from the base material upon which the alloy is plated.

A further object is to provide a method and means for obtaining an electroplated alloy of tungsten which is highly resistant to chemical attack, atmospheric oxidation, and the action of hot gases at high temperatures.

One more object is to achieve the foregoing with maximum economy and current efiiciency.

We have devised a unique process for electrodepositing alloys of tungsten upon an object which it is desired to so plate by making that object th cathode in a novel electrolytic bath. This bath is composed of an aqueous alkaline solution containing soluble salts from which are obtained: (a) tungstate ions; (b) ions of one or more of the iron group metals to be codeposited with tungsten; and (c) aliphatic organic ions containing at least three hydroxyl and carboxyl groups in sum total.

In operation, the bath is preferably maintained at a pH of between 7 and 10 and at a temperature ranging between 60 C. and 100 C. The electrodeposition is then accomplished by means of a current density of about 0.5 to amperes per square decimeter (amp./dm. of surface of the object being plated. Preferably, this current density should be between 0.5 and 10 amp./dm.

Code (1952),

depending somewhat upon the specific requirements and composition of the bath.

Problem to be solved The prior art has generally disclosed broad principles for electroplating alloys of various metals. However, efforts to satisfactorily electrodeposit alloys of tungsten, and in particular such alloys which include one or more metals of the iron group, have met with relatively little success. The deposits which such prior art techniques have provided generally have proved unsatisfactory due, for example, to the existence of flaws including pits, blemishes, inclusions and. cracks which appear in the structure of the deposit. Furthermore, the tungsten alloy thus plated has suffered from a tendency to peel from the base metal or otherwise exhibit poor properties of adhesion and cohesion.

Still other undesirable characteristics of the prior art tungsten alloy electroplates are those of low density, non-uniform composition or other irregularities and imperfections. In addition, the techniques by which those alloy electrodeposits have been accomplished are very complex and difficult to perform. For example, to obtain such tungsten alloy electrodeposits it has been neces-- sary to carefully select, combine and proportion the materials used in the electrolytic bath, and furthermore, to carefully control critical operating conditions including the baths pH, temperature and current density. Despite the elaborate methods which were developed for this purpose, the aforementioned unsatisfactory deposits resulted. One reason for this was that none of the methods apparently could prevent the irregular and uncontrollable deposition of one alloy constituent to the partial or entire exclusion of another.

The important problem which therefore has confronted workers in the electroplating field has been to provide an efiicient electrolytic process for the plating of materials with tungsten alloys in a manner which is relatively simple to operate. and the result of which is a uniform and highly satisfactory plated surface that satisfies all of the obgects set forth at the beginning of thi specifica ion.

Our improved electroplating bath Our invention has been extensively tested and found capable of solving the problem just outlined. Accordingly, by using electrolytic baths of the general character earlier described, we have been able very successfully to plate alloys of tungsten and on or more metals of the iron group 3 upon all forms or shapes of steel. objects including bars, wires, rods, plates, sheets, strips, tubes and other products of more intricate structure.

In supplying the tungstate ions necessary for our improved electroplating bath, we prefer to employ any one or a combination of two or more commonly available soluble tungstates. Examples of such materials which may be used are ammonium tungstate and tungstates of the alkali metals. In fact, it is probable that any other tungstate material may be used so long as it has no marked tendency to form an insoluble precipitate with other constituents of the bath or to react with the particular metal which is employed as the cathode.

The ions of the single alloying metal (iron, nickel or cobalt), or th ions of two or more of such metals to be co-plated with tungsten are supplied by introducing in the bath a soluble salt of the particular metals involved. This salt must be capable of supplying anions which are stable in solution, such as those of the metal chloride or sulphate, and they further must have substantially no detrimental effect on the deposition process taking place at the cathode.

The aliphatic organic ions which, as earlier mentioned, make up a part of our novel electrolytic bath, are supplied in the form of a soluble salt or salts of an hydroxy carboxyiic acid such as citric, tartaric, malic, gluconic or the like, of which the OH and CGOH groups amount to three or more in sum total, and the cations neither produce insoluble precipitates with all other constituents or" the bath nor do they react at the cathode. salts of any of these hydroxy carbox ylic acids which are suitable include those of potassium, sodium, ammonium, etc. rne organic material thus supplied essentially forms soluble complexes with one or more metals of the iron group in alkaline solution.

In addition to the bath constituents above referred to we have found iii-advantageous, although not essential, to include in the bath a quantity of one or more soluble ammonium salts of which the anions, like those previously referred to in describing the sources of iron group metal, are stable and have substantially no detrimental effect upon the cathode process. It should be understood that the ammonium salt material, for example ammonium chloride, is not an essential element of our improved electrolytic bath as is the aliphatic organic ion. However, the presence of an ammonium salt has been found to result in higher current eiliciencies and to aid in maintaining the metals of the iron group in solution. In some instances, particularly in those baths which include iron for co-deposition with tungsten, the smoothness of the resulting alloy deposits is notably improved by the presence of an ammonium salt in the bath.

Our experiments have showna number of striking examples of the efiect of ammonium salts in our alloy baths. Principal among these are the major increases in current efiiciency obtained with our unique baths from which are co-deposited either nickel-tungsten or cobalt-tungsten. In one instance, a certain nickel bath which originally contained citrates and tungstates but was devoid of ammonium. salts had a cathode current efficiency or less than 30%. After adding 50 grams per liter of ammonium chloride this efiiciency increased to 7 Similarly, the addition of ammonium salts to certain cobalt-tungsten-tartrate baths was found to maintain double the current efilciency, raising the value to about 4 In still another case involving a certain iron-tungsten-citrate bath the cathode current efficiency was raised from about 15% to 30% by a similar addition of ammonium salts.

It appears that-"the ammonium salts in the strong alkaline solution forms ammonia which in turn .forms amine complexes with the cobalt or nickel. These complexes are not in themselves sufficiently stable to hold up for long periods of time, but in the presence of the organic acid excellent stability is obtained. The effect is believed to result from the formation of a complex between the organic acid and the cobalt or nickel amine complex.

In addition to the just described flexibility which users of our inventive electrolytic baths and methods have at their disposal, still further variations of the procedure and materials may be employed with considerable success. For example, with respect to the concentrations of the metals in the bath which are to be deposited, the upper limit of their concentration should be at least slightly below the point of saturation so that substantial precipitation of those metals will not occur. The only lower limit on the concentration or bath metals which must be observed is that imposed by practical considerations of the economy of time.

In practicing our invention we have observed that when a relatively small amount of the plating metal is in the bath the process is considerably slowed up and a lower current density is required. To meet most practical purposes, approximately 2 grams per liter of bath solution may be taken as the lower limit of concentration for the metal or metals of the iron group, and 5 grams per liter for the lower concentration limit of tungsten. The lowest practical concentration of the aliphatic organic compound should be the minimum quantity which will safely keep the alloying iron group metal in solution; that is, an amount which will prevent substantial precipitation.

Repeated tests of our novel plating method and baths have shown that the percentage of tungsten in the electrolytic deposits which can be obtained increases with current density when all other conditions of operation are maintained substantially constant. We also find that an increase in the ratio of aliphatic organic acid to the iron group metal in the bath increases the percentage of tungsten in the resultant deposit, while an increase by weight in the ratio of tungsten to the iron group metal beyond a ratio or 2:1 only slightly increases the percentage of tungsten in the deposits obtained at a given current density.

As was previouslymentioned, ammonium salts may optionally be included in the electrolytic bath. Those salts do not materially affect the composition or the electrodeposited alloy, but we have observed that they are definitely instrumental in the obtainment of certain advantages such as higher current efficiencies and in maintaining the 'metals'of the iron-group in solution.

Electrodcposition of nickel-tungsten alloy Typically illustrative of the manner in which our invention may be practiced is the electroplating of a steel object with nickel-tungsten alloy. To accomplish such plating an alkaline electrolytic bath is provided in a suitable container, said bath approximately consisting of the following constituents: 26 grams/liter nickel chloride (NiC12.6H2O); '70 grams/liter sodium scams tungstate (Na2WO4.2I-I2O); 100 grains/liter sodium citrate; and a remainder consisting of water. In some cases, where the alkalinity of the bath requires adjustment, certain materials such as ammonium hydroxide may help make up the balance of the bath instead of just plain water.

A preferable procedure which insures the obtainment of a satisfactorily adherent plate of nickel-tungsten alloy is to clean the steel objectto-be-plated prior to the plating process. One suitable method for doing this is to make that steel object the anode in an electrolytic bath containing about 70% sulphuric acid, and subjecting the object being thus cleaned to this treatment for two to five minutes at about 25 amperes per square decimeter of surface of the immersed steel object. Optionally, however, other techniques of cleaning may be employed. Whatever method is used the cleaned object should preferably be rinsed in fresh clean water before plating the alloy thereon.

The clean object-to-be-plated is made the cathode and immersed in the plating bath. For the anodes we prefer to use bagged nickel and/or tungsten instead of the insoluble type of anode. This preference is due to the fact that, in general, insoluble anodes tend to oxidize the aliphatic organic acid salt and may lead to poor adhesion, cracking and exfoliation of the deposit.

To operate this electrolytic bath we employ sufficient direct current so as to provide an operating current density of about 5 amperes per square decimeter of immersed surface of the object to be plated. In operation the bath temperature is maintained at about 90 C. by means of any suitable source of heat, while the pH of the bath is regulated to be approximately 8 or 9. Control of this pH may satisfactorily be had by the addition of ammonium hydroxide to the plating solution.

Under the above described conditions of operation the nickel-tungsten all-0y will plate out on the steel cathode with a cathode current efliciency ranging in the neighborhood of about 70%. The electrode'posited alloy gains a thickness of approximately 0.001 inch in about 50 minutes and in four hours reaches a thickness of about 0.005 inch. This deposition may be continued until the desired thickness of deposit has been obtained, when the product being plated is then withdrawn from the bath to be rinsed and dried preparatory to its desired use. If preferred, the plated product may be given further treatment such as various heat treatments or polishing.

Our novel method has been found capable of satisfactorily. electrodepositing tungsten alloys on a confined area of a given object, such as on the interior of a steel tube. In thus applying our invention certain precautions should be taken to insure adequate circulation of the bath fluid adjacent the confined area that is to be plated. Otherwise, the bath tends to become depleted due to confinement of the fluid within the tube or other object, and the deposit tends to become nodular as Well. For best results in this particu-: lar application of our invention, therefore, we prefer to bubble air through the interior of tubes and the like that are to be so plated. One means of conveying air in this manner is to use an air pump while the plating operation is in progress.

Another detail to be observed in applying our invention to the plating of bores of tubes, etc., is

to employ soluble anodes, as for example, of

tungsten, rather than of an iron group metal.

acid to adjust the pH to about 1.

The reason for this is that the forced circulation of bath fluid tends to avoid passivation of the soluble anodes and thus keeps a fresh supply of alloy metals at all times adjacent the confined area being plated.

Another valuable discovery which helps to improve the results that may be obtained in practicing our invention is the important bearing which the ratio between amounts of metallic nickel to the citrate compounds in the bath has upon the quantity of tungsten deposited therefrom. In the plating process hereinbefore described for the nickel-tungsten bath, the resulting deposit contains about 25% tungsten while the remainder is substantially nickel. That alloy was found to have a hardness of approximately 600 Micro-Vickers prior to heat treat- .ment, and about 700 Micro-Vickers after being subjected to an anneal at 600 C. for about one hour.

By lowering the amount of citrate present in the bath we have observed that less and less tungsten appear in the alloy deposit. For example, in one case we used 6 grams of nickel and. 30 grams of sodium citrate per liter, or just enough citrate to keep the nickel in solution; the result was that only very small quantities of tungsten were co-deposited with nickel. Yet, with the same amount of nickel but with grams per liter of sodium citrate, the alloy which Was co-deposited contained approximately 35% of tungsten.

We also have experimented in varying the tungsten content of the bath, as from 18 to 100 grams per liter. In no case have We noted any great influence of this variable on the composition of the resulting deposit.

Alloys of tungsten with other iron group metals In general, the cobalt-tungsten and irontungsten baths behaved similarly to the nickeltungsten baths which have just been described. The same appears to be true of baths which con tain sources of tungsten and two or more metals of the iron group for depositing ternary and quaternary alloy metal.

As earlier mentioned, We have found that the nickel-tungsten alloys deposited in accordance with our processes adhere satisfactorily to clean steel or to steel which has been given the aforementioned sulphuric acid anodic treatment prior to the plating operation. The cobalt-tungsten alloys, however, do not adhere in the highest degree to hard steels, such as gun steels, without the use of a strike solution. (The general purpose for using a strike solution is Well known to the prior art, conventionally consisting of a special bath used in addition and prior to the main plating bath and operation. The strike solution normally ha special conditions such as a low concentration of the 'metal to be plated therefrom, and is used merely to get the first covering of that metal on the object to be plated, after which additional amounts of the metal are built up on the object in the regular plating solution.)

The strike" operation preferably is performed subsequent to any required cleaning step but prior to the actual plating operation. A satisfactory strike bath is an aqueous solution containing about 20 grams per liter of cobalt-chloride or cobalt-sulphate and enough hydrochloric The object-tobe-plated is made the cathode in the strike bath and is treated for approximately one-half minute while maintaining .a current density of about 10 amperes per square 'dec'imeter of .that catho'des immersed surface.

Electrodeposition of cobalt-tungsten ailloy A preferred bath which we employ in co-depositing cobalt and tungsten metal comprises .approximately the following amounts ,per liter: '70 grams sodium tungstate (NazWOaZHzO) '28 grams cobalt chloride (.CoClafiI-IzO); 100 grams Zochelle salt; 50 grams .ammonium chloride; and the remainder substantially all water except for such supplemental materials .as ammonium hydroxide which maybe required for adjusting the alkalinityof the bath.

For highly satisfactory. results, this particular bath should be operated at a temperature of about 90 C. and at a current density. of approximately 1 to '3 amperes per square decimeter .of immersed surface of the work to be ,plated. It is also preferable to maintain the bath :at a .pH of about 8 or 9 during the plating treatment. For anodes we prefer to use cobalt and/or tungsten.

With this compos'itionof bath and under the conditions of operation just mentioned, .a cathode current efiiciency ranging between approximately 80 and "95% prevails. The deposits -of cobalt-tungsten alloy whichv we 'haveobtained by thedes'cribed method .and bath have ahardness of about '500 to 600 'Micro-Vickers when taken from the electrolytic bath, and are hardenable to approximately 900 to 1000 Micro-.Vickers .by heating at .a temperatureof about.6.00.C. for approximately one-'hal'fihour.

Electrodeposition "of iron-tungsten alloy For electrodepositing iron-.tungstenalloy metal we have found a satisfactory plating bath to comprise the following amounts per liter: '70 "grams sodium tungstate -(Na2WO4.-2H2O); *8 grams of ironin'the form of sulphateor chloride; 100 grams sodiumcitrate; -50-grams am- -monium chloride; and the remainder substantially all-water-except for a -suflicient quantity of ammonium hydroxide or the-like "which may be necessary to adjust the pH of the bath to about 8- or' 9.

' We have found that this bath gives particularlygood results'whenoperated at a temperature of about90-C. and within a current density range of'approximately 2- to amperes-per square decimeter of the immersedsurface of the-object to be plated. The iron-may besupplied' to the bath from either ferric or ferrous iron compounds, although in general, the ferric compounds are preferable because they are "more soluble and thus permit higher concentrations of iron in the bath.

We have further-"observed, howeventhat as the bath is operated an equilibrium reached with respect to ferric-andferrous iron. In view of this, it is preferred to' make up the bath'with about-half of the iron in'the"ferric"stateiand about half in the ferrousstate. This is particularly advisable when soluble anodesof tungsten are to'be'used .in conjunction with 'the' bath.

Under these conditions the half -and.-ha1f protungst'en alloy contains about 50% tungsten and has a hardness of approximately 700- to 900 Micro-Vickers. This allow may, however, 'be hardened to between 1200 and 1400 Micro-Vickers by heating at a temperature of 600 C. for about one-half hour. As is typical of the broad applications made possible by our invention, the ratio of tungsten to :iron in the iron alloy plating ibaths may be varied over wide limits to secure deposits of varying compositions. Under conditions of operation similar to those above described, an iron-"tungsten bath comprising 35 grams of tungstenand'oz gra'm'of iron per liter was found to give a deposit containing about 65% tungsten; while a bath comprising-0.1 gram of tungsten'and Bgrams of iron per liter gave an alloy deposit containing about 7% tungsten.

In general, it may be said that the iron alloy baths give deposits having higher percentages of tungsten'than areobtainable from the earlier described nickel-tungsten or cobalt-tungsten baths. The iron-tungsten alloy deposits .also have greater hardness properties than do the alloys of nickel tungsten and cobalt-tungsten. On the other hand, however, the cobalt-tungsten baths customarily have the highest cathode current efficiency in comparison with the nickeltungsten and iron-tungsten baths.

Summary .up to for the cobalt alloy, andup to for the iron alloy, depending upon theconditions of deposition. Within the rangeof depositcompositions noted, the several elements present form. a true alloy metal, as true alloys arecommonlyydefined. The depositsaredense, and in general, are highlyadherent and quite resistant ,to mechanical-removalfrom theunderlying parentmetal. Itis also important to note thatthe .electroplates which we obtain by our invention are resistant to. chemical attack, atmospheric oxidation and the action of hot gases atlhigh temperatures and pressures.

Thus it,,will further beseen thatv by. .our inventionwe have provided .a simple, direct and highly effective method for ,electrodepositing tungsten in alloys with metal or metals of the iron group;

thatxwe have. provided suitable, baths for the electrodepositionlof tungsten inalloy with one or ,more metals. of .theiron group andwhich are characterized by high current .efficiency, good throwing power and stabilityinoperation; that we have provided-a reliable method and means forobtaining the. electrodeposition of ,atungsten ,alloy. of uniform thickness, and composition, and .whosesurface isv free. of nodules, pits or blem- .ishes;

that .we have provided a method and means .for obtaining anelectroplated alloy. of

tungsten which possesseshigh, cohesive and ad- .hesive ,propertiesand therefore ,will not-peel .fronrthe base materialupon which the alloy is .plated; that ,Wehave provided a method and meansfor obtaining .anelectroplated alloy, of

tungsten which, is highly resistantt chemical attack, atmospheric oxidation and the action I of .hotgases at high temperaturesnand that we haveachieved the foregoing With maximumeconomy and current efiiciency.

I Although a number of possible embodiments of our invention have been described, it will be quite obvious to those generally skilled in the art that a number of modifications of our general method and in the specific elements mentioned for use in our electrolytic bath may be employed without departing from the spirit and intent of our'invention. It should therefore be understood that the matter described herein is to be interpreted as being merely illustrative and not as any necessary limitation.

Our invention is therefore extensive in its adaption and'is not to be restricted to the form here disclosed by way of illustration.

solution of soluble salts that supply to said solution tungstate ions and a complex consisting of ammonium ions plus ions of at least one metal of the group consisting of iron, cobalt and nickel, plus aliphatic organic ions having at least three hydroxyl and. carboxyl groups in sum total, said soluble salts being substantially non-reactive chemically with the said metal object upon which the tungsten alloy is being electroplated, and plating said metal object with the tungsten al- 10y.

2. The method of electroplating a metal objectwith' an alloy composed of tungsten and at least one metal of the group consisting of iron, cobalt and nickel; which method comprises connecting the object to be plated as a cathode in an electrolytic bath consisting of an aqueous alkaline solution of soluble salts that supply to said solution tungstate ions and a complex consisting of ammonium ions plus ions of a least one metal of the group consisting of iron, cobalt and nickel, plus aliphatic organic ions having at least three hydroxyl and carboxyl groups in sum total, said soluble salts being substantially non-reactive chemically with the said metal object upon which the tungsten alloy is being electroplated; maintaining said solution at a pH within the approximate limits of about '7 to 10 and at a temperature ranging from about 60 C. to about 100 C.; and passing an electric current through said electrolytic both to cause the electroplating of a tungsten alloy upon said metal object.

3. The method of electrodepositing upon a metal object an alloy composed of tungsten and at least one metal of the group consisting of iron, cobalt and nickel; which method comprises connecting the said metal object as a cathode in an electrolytic bath consisting of an aqueous alkaline solution of soluble salts that supply to said solution tungstate ions and a complex consisting of ammonium ions plusions of at least one metal of the group consisting of iron, cobalt and nickel, plus ions from an aliphatic series hydroxy carboxylic acid of which the OH and COOH cations amount to at least three in sum total, said cations neither producing insoluble precipitates with any of the other constituents of said solution nor reacting with the metal which constitutes the said object upon which the tungsten alloy is being electrodeposited, and electrode positing the tungsten alloy upon said metal object.

4. The method of electrodepositing upon a metal object an alloy composed of tungsten and r a 10 at least one metal of the group consisting of iron, cobalt and nickel; which method comprises connecting the said metal object as a cathode in an electrolytic bath consisting of an aqueous alkaline solution of soluble salts that supply to said solution tungstate ions and a complex conisting of ammonium ions plus ions of at least one metal of the group consisting of iron, cobalt and nickel, plus ions from an aliphatic series hydroxy oarboxylic acid of which the OH and COOH cations amount to at least three in sum total, said cations neither producing insoluble precipitates with any of the other constituents of said solution nor reactive with the metal which constitutes the said object upon which the tungsten alloy is being electrodeposited; maintaining said solution at a pH within the approximate limits of about 7 to 10 and at a temperature ranging from about 60 C. to about C.; and passing an electric current through said electrolytic bath at a current density of about 0.5 to about 40 amperes per square decimeter of surface of the said object upon which the tungsten alloy is being electrodeposited.

5. The method of electroplating a metal object with an alloy composed of tungsten and at least one metal of the group consisting of iron, cobalt and nickel; which method comprises connecting the object to be plated as a cathode in an electrolytic bath consisting of an aqueous alkaline solution of materials that supply to said solution tungstate ions and a complex consisting of ammonium ions plus ions of at least one metal of the group consisting of iron, cobalt, and nickel, plus aliphatic organic ions having at least three hydroxyl and carboxyl groups in sum total, plus alkali metal ions, said materials in the solution being substantially non-reactive chemically with the metal which constitutes the said object upon which the timgsten alloy is being electrodeposited.

6. The method of electroplating a metal object with an alloy composed of tungsten and at least one metal of the group consisting of iron, cobaltand nickel; which method comprises connecting the object to be plated as a cathode in an electrolytic bath consisting of an aqueous alkaline solution of materials that supply to said solution tungstate ions and a complex consisting of ammonium ions plus ions of at least one metal of the group consisting of iron, cobalt and nickel, plus aliphatic organic ions having at least three hydroxyl and carboxyl groups in sum total, plus alkali metal ions, said materials in the solution being substantially non-reactive chemically with the metal which constitutes the said object upon which the tungsten alloy is being electrodeposited; and maintaining said solution during the electroplating operation at a pH of about '7 to 10 and at a temperature ranging from about 60 C. to about 100 C.

7. The method of electroplating an object with an alloy composed of tungsten and at least one metal of the iron group consisting of iron, cobalt and nickel; which method comprises connecting the object to be plated as a cathode in an aqueous alkaline electrolytic bath solution containing a tungstate and a complex consisting of ammonia and a salt of an aliphatic series hydroxy carboxylic acid of which the OH and COOH cations amount to at least three in sum total and at least one metal of the group consisting of iron, cobalt and nickel, and plating upon said object an alloy of tungsten and the metals of the iron group in said bath.

aesa es 8. The method of electroplating an object with an alloy composed, fo tungsten and at least one metal of the iron group consisting of iron, cobalt and. nickel; which method comprises connecting the object to be. plated as a cathode in an aqueous alkaline electrolytic bath solution containing a tungstate and a complex consisting of ammonia and a salt of at least one acid of the group consisting of tartaric, malic, gluconic and citric acids, and at least one metal of the group consisting of iron, cobalt and nickel, and plating upon said object an alloy of tungsten and the metals of the iron group in said bath.

9. As a bath for the electrolytic co-deposition of tungsten with at least one metal of the group consisting of iron, cobalt. and nickel, an aqueous alkaline solution. which. includes a tungstate and a complex consisting; of. ammonia and a salt of an aliphatic; series hydroxy carboxylic acid of which the. 01-1 and COOH cations amount to at least three in sum total and. at least one metal of the group consisting of iron, cobalt and. nickel, said solution being substantially non-reactive chemically with the metal which constitutes the said object upon which the tungstenalloy is being electrodeposited.

10. As a bath for the electrolytic co-deposition of tungsten with at least one metal of the group consisting of iron, cobalt and nickel, an aqueous alkaline solution which includes a tungstate and a complex consisting of ammonia and a salt of at least one acid of the group consisting of tartaric, malic, g-luconic and" citric acids and at least one metal or" the group consisting of iron, cobalt and nickel, said solution being substantially nonreactive chemically with the. metal which constitutes the said object upon which the tungsten alloy is being electrodeposited.

11. The method. of regulating the amount of tungsten which electrolytically co-deposits upon an object with at least one metal of the iron group consisting of. iron, cobalt and nickel; which method, comprises connecting the object to be plated in an electrolytic. bath, consisting of an aqueous alkaline solution of materials that supply to said. solution tungstate ions and a complex consisting of ammonium ions, plus, ions of at least one. of the iron group metals in the bath, plus al'pihatic. organic ions having at least three hydroxyl and carboxyl. groups in sum total, said materialsin the' solution being substantially nonreactive chemically with the. object to be plated; then reasing the ratio of aliphatic organic ions tov ions of the from. group metals. in. the bath. when it is v desired to. increase the relative amounts. of. tungsten which co.- deposits. therefrom with the respective. irongroup metals; and of decreasing the ratioof aliphatic. organic ionsv of the iron group. metals in. the bath when it is desired to decrease the relative amounts of tungstenwhich co-deposits therefrom with the respective iron group, metals.

12. The method of regulating the amount of tungsten which electrolytically co-deposits with nickel upon. an. object; which method comprises connecting the. object to be plated in an electrolytic bath consisting; of an, aqueous alkaline solution of materials that supply to said solution soluble. citrates, tungstates, and a complex consisting of ammoniumv ions anda nickel salt; then increasing; the. ratio of citrate to. nickel compounds in, the bathwhen it is desired to increase the relative amounts of tungsten which co-deposits. therefrom. withnickeh, and decreasing the ratio of citrate to nickel. compounds in the bath when. it is desired to. decrease the relative amounts of tu-ngstenwhich-co-deposits therefrom with nickel.

ABNER BRENNER. POLLY S. BURKHEAD. CLARA A. SENTEL.

References Cited in the file of this patent UNITED- STATES PATENTS Number Name Date 2,160,321 Armstrong et al. May 30, 1939 2,160,322 Armstrong'et al. May 30, 1939 FOREIGN PATENTS Number Country Date 460,931 Great, Britain Feb. 1, 1937 ()TI-IER- REFERENCES Yntema, Journal. American Chemical Society, vol. 54: (1932) ,,pD..377,5-6,

Fink etzaL, Transactions Electrochemical Soc, vol. 59 (1931), pp. 461-81.

Vaaler et, al., Transactions Electrochemical Soc.,vo1. 9011947), Dp..43-54.

Goltz et. al., Journal. Applied Chemistry (U. S. S. R.), vol. 9. (19.36.), p. 640.; Chem. Abstr., vol. 30. (1936), p..'7460..

Belyaev et al., Korroziya i Borba s Nei, vol. 6, No. 2 (19.40,), p. 417; Chem. Abstr., vol. 36 (19 12), p-3735. 

1. THE METHOD OF ELECTROPLATING A METAL OBJECT WITH AN ALLOY COMPOSED OF TUNGSTEN AND AT LEAST ONE METAL OF THE GROUP CONSISTING OF IRON, COBALT AND NICKEL; WHICH METHOD COMPRISES CONNECTING THE OBJECT TO BE PLATED AS A CATHODE IN AN ELECTROLYTIC BATH CONSISTING OF AN AQUEOUS ALKALINE SOLUTION OF SOLUBLE SALTS THAT SUPPLY TO SAID SOLUTION TUNGSTATE IONS AND A COMPLEX CONSISTING OF AMMONIUM IONS PLUS IONS OF AT LEAST ONE METAL OF THE GROUP CONSISTING OF IRON, COBALT AND NICKEL, PLUS ALIPHATIC ORGANIC IONS HAVING AT LEAST THREE HYDROXYL AND CARBOXYL GROUPS IN SUM TOTAL, SAID SOLUBLE SALTS BEING SUBSTANTIALLY NON-REACTIVE CHEMICALLY WITH THE SAID METAL OBJECT UPON WHICH THE TUNGSTEN ALLOY IS BEING ELECTROPLATED, AND PLATING SAID METAL OBJECT WITH THE TUNGSTEN ALLOY. 